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Nicotine Addiction

Unlike most drugs, the negative health effects of
nicotine are long-term. Even so, the overall cost of nicotine addiction
to individuals and to the community is astronomical!

Statistics from the Centers for Disease Control
and Prevention indicate that tobacco use remains the leading
preventable cause of death in the United States, causing approximately
440,000 premature deaths each year and resulting in an annual cost of
more than $75 billion in direct medical costs attributable to smoking.

Over the past four decades, cigarette smoking has
caused an estimated 12 million deaths, including 4.1 million deaths
from cancer, 5.5 million deaths from cardiovascular diseases, 2.1
million deaths from respiratory diseases, and 94,000 infant deaths
related to mothers smoking during pregnancy.

Secondhand smoke, also known as environmental
tobacco smoke, is a mixture of the smoke given off by the burning end
of tobacco products (side stream smoke) and the mainstream smoke
exhaled by smokers. It is a complex mixture containing many chemicals
(including formaldehyde, cyanide, carbon monoxide, ammonia, and
nicotine), many of which are known carcinogens.

Non-smokers exposed to secondhand smoke at home or
work increase their risk of developing heart disease by 25 to 30
percent and lung cancer by 20 to 30 percent.

In addition, secondhand smoke causes respiratory
problems in nonsmokers such as coughing, phlegm, and reduced lung
function. Children exposed to secondhand smoke are at an increased risk
for sudden infant death syndrome, acute respiratory infections, ear
problems, and more severe asthma.

Since 1964, 28 Surgeon General's reports on
smoking and health have concluded that tobacco use is the single most
avoidable cause of disease, disability, and death in the United States.
In 1988, the Surgeon General concluded that cigarettes and other forms
of tobacco, such as cigars, pipe tobacco, and chewing tobacco, are
addictive and that nicotine is the drug in tobacco that causes
addiction.

Nicotine provides an almost immediate "kick"
because it causes a discharge of epinephrine from the adrenal cortex.
This stimulates the central nervous system and endocrine glands, which
causes a sudden release of glucose. Stimulation is then followed by
depression and fatigue, leading the user to seek more nicotine.
Nicotine is absorbed readily from tobacco smoke in the lungs, and it
does not matter whether the tobacco smoke is from cigarettes, cigars,
or pipes. Nicotine also is absorbed readily when tobacco is chewed.

With regular use of tobacco, levels of nicotine
accumulate in the body during the day and persist overnight. Thus,
daily smokers or chewers are exposed to the effects of nicotine for 24
hours each day. Adolescents who chew tobacco are more likely than
nonusers to eventually become cigarette smokers.

Addiction to nicotine results in withdrawal
symptoms when a person tries to stop smoking. For example, a study
found that when chronic smokers were deprived of cigarettes for 24
hours, they had increased anger, hostility, and aggression, and loss of
social cooperation. Persons suffering from withdrawal also take longer
to regain emotional equilibrium following stress. During periods of
abstinence and/or craving, smokers have shown impairment across a wide
range of psychomotor and cognitive functions, such as language
comprehension.

Women who smoke generally have earlier menopause.
Pregnant women who smoke cigarettes run an increased risk of having
stillborn or premature infants or infants with low birth weight.
Children of women who smoked while pregnant have an increased risk for
developing conduct disorders. National studies of mothers and daughters
have also found that maternal smoking during pregnancy increased the
probability that female children would smoke and would persist in
smoking.

In addition to nicotine, cigarette smoke is
primarily composed of a dozen gases (mainly carbon monoxide) and tar.
The tar in a cigarette, which varies from about 15 mg for a regular
cigarette to 7 mg in a low-tar cigarette, exposes the user to an
increased risk of lung cancer, emphysema, and bronchial disorders. The
carbon monoxide in tobacco smoke increases the chance of cardiovascular
diseases. The Environmental Protection Agency has concluded that
secondhand smoke causes lung cancer in adults and greatly increases the
risk of respiratory illnesses in children and sudden infant death.

Research has shown that nicotine, like cocaine,
heroin, and marijuana, increases the level of the neurotransmitter
dopamine, which affects the brain pathways that control reward and
pleasure. Scientists have pinpointed a particular molecule [the beta 2
(b2)] subunit of the nicotine cholinergic receptor as a critical
component in nicotine addiction.

Mice that lack this subunit fail to
self-administer nicotine, implying that without the b2 subunit, the
mice do not experience the positive reinforcing properties of nicotine.
This finding identifies a potential site for targeting the development
of nicotine addiction medications. Other research found that
individuals have greater resistance to nicotine addiction if they have
a genetic variant that decreases the function of the enzyme CYP2A6. The
decrease in CYP2A6 slows the breakdown of nicotine and protects
individuals against nicotine addiction.

Understanding the role of this enzyme in nicotine
addiction gives a new target for developing more effective medications
to help people stop smoking. Medications might be developed that can
inhibit the function of CYP2A6, thus providing a new approach to
preventing and treating nicotine addiction. Another study found
dramatic changes in the brain's pleasure circuits during withdrawal
from chronic tobacco use. These changes are comparable in magnitude and
duration to similar changes observed during withdrawal from other
abused drugs such as cocaine, opiates, amphetamines, and alcohol.

Scientists found significant decreases in the
sensitivity of the brains of laboratory rats to pleasurable stimulation
after nicotine administration was abruptly stopped. These changes
lasted several days and may correspond to the anxiety and depression
experienced by humans for several days after quitting smoking "cold
turkey."

The results of this research may help in the
development of better treatments for the withdrawal symptoms that may
interfere with individuals' attempts to quit.